I'm going to go against the grain here. Yellowing lower leaves means that the plant is low on nitrogen. What's happening is the plant is pulling nitrogen out of the lower leaves to feed the new growth at the top. I'm guessing that your fert dose is a bit too low. Also, 1 gallon isn't enough anymore. I'd transplant them using the same organic soil into 5 gallon buckets or something similar. That will probably be enough soil space for the duration. Flowering for 27 days and getting nothing in response from a plant isn't right. I don't know what the instructions are for your fert but follow that and give a dose once you transplant them. Ferts don't cause plants to flower. It's the light cycle that does that. They need phosphorus to flower, but that's not the cause. The light cycle cause a plant's hormones to change from veg cycle to flower. Personally, for a soil grow, I wouldn't worry much about pH right now.